Compared to conventional LCD panels, AMOLED (Active-matrix organic light emitting diode) display screens have characteristics, like fast response, higher contrast and wider view. Because of current driving characteristics of an OLED (Organic Light Emitting Diode), a pixel circuit has a plurality of TFT (Thin Film Transistor) and a plurality of capacitors thereon, for example, a circuit structure as shown in FIG. 1, and a schematic diagram of a corresponding pixel arrangement as shown in FIG. 2.
Currently, due to the increasing requirements for display performance, those skilled in the art have made various improvement attempts to enhance the display performance with respect to the design of the pixel circuit. For example, as shown in FIG. 3, in order to improve the risk of short circuit caused by metal profile in a via hole resulting from the anode and cathode in OLED connected though the via hole, a pixel defining layer is usually employed to fill the via hole for connecting the cathode to the anode, as shown in FIG. 4, however, this may cause a reduced aperture ratio. It is noted that, in practice, the cathode and anode in FIG. 3 and FIG. 4 further comprise therebetween other layers not shown in the drawings, such as a light emitting layer and the like.
In another example, to further improve the display performance, the number of pixels in unit area can be increased, but this may lead to a problem of small capacitance. The capacitance may be increased in the art by providing an additional Metal3 (a metal which does not belong to a gate metal layer or source-drain metal layer) in a display substrate. For example, by adding a Metal3 as shown in FIG. 6 on the basis of the structure of the display substrate shown in FIG. 5 can increase the capacitance. However, still there will be a problem of lower aperture ratio.
In summary, in order to compensate for the shortcomings of the pixel structure, it would inevitably lead to a decrease in the aperture ratio of the display panel, as well as to white light OLED (WOLED).